This invention relates generally to electric soldering instruments and more specifically to replaceable soldering tips for hand held soldering irons.
In the current state of the soldering art where light weight, electrically efficient, precision temperature controlled, and versatile hand held soldering irons are used in electronic production, research and development, maintenance and repair, and hobbyist activities, it is routinely desirable to exchange soldering tips, for example, for purposes of replacement for wear, selection of shape for specific tasks, or selection for power handling capability.
A currently preferred configuration for such soldering requirements includes an elongated cylindrical ceramic rod or tube which is supported and projects forwardly from the soldering iron handle. The forward few centimeters of the ceramic body carries the electric heating element and temperature sensor means which may be a separate thermistor element or may be the heating element itself used in a time-share mode to sense temperature or a function of its electrical resistance. The electrical heating element is typically deposited as a very thin patterned layer onto the outer surface of the ceramic body.
It is then the general practice to fit a soldering tip over the heater portion of the rod in a manner to carry thermal energy from the heater to the forward, working end of the soldering tip. To maximize such thermal transfer, the skirt of the soldering tip extends snugly over the ceramic rod for approximately the length of its heater portion.
Obviously, the ceramic rod and especially the thin, deposited heating element are significantly fragile with respect to impact and abrasion, respectively. Accordingly, it is difficult to provide a snug fitting, slidingly removable soldering tip which is close fitting to provide maximum heat transfer into itself from the heating element while not subjecting the ceramic rod and heating element to damage when removing or replacing it. Furthermore, the problem is severely aggravated by the accumulation of corrosion and decomposition products on the inner surface of the soldering tip which reduce or destroy any of the designed small clearance between the heating rod and the soldering tip. In addition, these products are typically adhesive and may, under some circumstances, bind the tip and heater together. As a result, a tip designed for a snug but free fit over the ceramic heater rod will, after use, cause damage to the heater when one attempts to remove and replace it.
Prior art approaches to the problem typically comprise different attempts to optimize between 1) designing the tip for a snug, thermally efficient fit with its attendant risks of damage to the heater and 2) providing a safely loose fit with its attendant poor thermal transfer characteristic.
A second approach has been to provide some adjustment in the snugness of fit by providing a soldering tip with a skirt of relatively large inner diameter so that there is small risk of damaging the heater element by its replacement. Its thermal efficiency is then improved by splitting and slotting the base of the soldering tip skirt and providing a small peripheral clamp around the slotted base of the skirt so that a region of tight thermal contact is provided. This technique, however, provides only a small region of thermal contact and it is at the end of the soldering tip most remote from its working end. Furthermore, the clamp is often an awkward encumbrance for the operator to deal with during precision soldering tasks. In addition, the supply of suitable clamps and their removal and replacement constitute additional steps and cause their own complications when exchanging soldering tips.
Accordingly, it is an object of the present invention to provide a replaceable soldering tip assembly which is not subject to these and other disadvantages and disadvantages and limitations of the prior art.
It is another object to provide such a system in which the soldering tip has a maximum thermal energy transfer relation to the soldering heater without risk of damaging the latter during removal or replacement of the tip.
It is another object to provide such a tip assembly which requires no separate clamps or similar such devices to achieve good thermal contact between heater and tip.
It is another object to provide such a tip assembly in which the tip may be exceedingly easily replaced even if heavily corroded or spent.
It is another object to provide such a tip assembly which is rugged, simple, and which may be inexpensively manufactured with no regard for difficult machining or plating tolerances.